Locally curated URL lists elicit 3–5× higher blocking rates than global lists in high-censorship countries. In China and Yemen, local content was blocked three to five times more than globally sensitive content, attributed to language filtering and active censorship of local political discourse; China's 99% block rate on 'falun' in HTTP path vs. 81% for 'falun' in domain name further illustrates trigger sensitivity.

Residential ISP vantage points detect 36% more blocking than academic networks: of 1,947,691 matched URL tests, 72,454 non-academic tests were classified as blocking versus 52,921 academic tests. Averaged across 10 countries, the Jaccard similarity between blocked-URL sets in academic vs. non-academic networks is 0.59, indicating substantial divergence.

§5.3, Fig. 12 evaluation

Iran's censorship infrastructure shifted from fully decentralized (Jaccard similarity ~0 across ISPs in 2007) to highly centralized by June 2011, when the Jaccard similarity between the national gateway AS 12880 and two other ISPs reached 0.94 and 0.95. Almost all 2011 blocking was accompanied by a blockpage containing an iframe redirecting to internal IP 10.10.34.34, providing direct evidence of a single choke-point filtering infrastructure.

§4.5, Table V detection

Across MENA countries (UAE, Tunisia, Oman, Iran, Qatar, Yemen, Saudi Arabia, Burma), over 80% of blockpage-delivering tests delivered the blockpage without DNS redirection, indicating transparent web proxies performing deep HTTP inspection rather than the cheaper DNS-intercept approach dominant in China. McAfee SmartFilter was identified in Qatar, Saudi Arabia, and UAE; Netsweepr in Qatar, UAE, and Yemen.

§5.1, Table VI evaluation

Yemen's national ISP (YemenNet) uses explicit blockpages for social and Internet-tools content while applying stealthy techniques — TCP RST injection and unrequited HTTP GETs — specifically for political and conflict content that is constitutionally protected. Censorship also ceases intermittently when the ISP exhausts filtering product licenses.

§4.2, Fig. 6 detection

GFWeb tested 1.02 billion domains against the GFW over 20 months and discovered 943,000 pay-level domains blocked by HTTP filters and 55,000 by HTTPS filters — the largest GFW blocklist dataset ever published. The HTTP-to-HTTPS ratio (17:1) confirms that the GFW's HTTPS keyword-based and SNI-based blocking covers far fewer domains than its HTTP host-header blocking, likely because HTTPS blocks carry higher collateral-damage risk.

2024-hoang-gfweb Abstract, §5.1 dpidns-poisoningip-blockingkeyword-filteringsni-blocking

The largest measurement study of Turkmenistan censorship to date tested 15.5 million domains and found more than 122,000 domains censored using separate blocklists for DNS, HTTP, and HTTPS. Reverse-engineering the blocking rules revealed approximately 6,000 over-blocking rules that cause incidental filtering of more than 5.4 million additional domains — a 44x collateral damage ratio relative to intentionally blocked domains.

2023-nourin-measuring §Results dns-poisoningdpikeyword-filteringip-blocking

Extending Geneva's genetic algorithm to the application layer automatically discovered 77 unique HTTP evasion strategies and 9 DNS evasion strategies against censors in China, India, and Kazakhstan — all requiring only unprivileged usermode modifications with no TCP/IP header access. Against India's Airtel censor, 56 of the 77 strategies succeeded; 29 worked against Kazakhstan; 22 evaded China's keyword-based HTTP censorship and 27 evaded its Host-header censorship.

2022-harrity-get §5.1, §6 dpikeyword-filteringrst-injectiondns-poisoning

Despite Russia's decentralized ISP ecosystem, 9 of 14 residential probes observed more than 90% of 98,098 tested blocklist domains blocked, and all 14 probes observed at least 49% blocked—demonstrating that coordinated nationwide censorship without centralized choke-points is achievable through legal mandates and commodity equipment alone.

2020-ramesh-decentralized §VI-B ip-blockingdns-poisoningkeyword-filteringdpi

Autosonda classified 76 commercial web filters in the NYC metropolitan area into three categories: 21 (27.63%) performed DNS blacklist filtering, 44 (57.89%) matched on the HTTP Host header of GET requests, and 11 (14.47%) performed a DNS lookup of the Host header value and blocked based on the resulting IP. Autosonda found circumvention paths for 100% of filters tested.

2017-jermyn-autosonda §4.1 Results dpidns-poisoningkeyword-filtering

China's Internet censorship ecosystem is bilateral: the GFW handles technical blocking while separate government agencies (MIIT, TCA, MPS, MSS) handle non-technical regulation, and 'these two components do not operate synchronously.' Google Scholar is considered a legal service by Chinese regulators but is incidentally blocked as collateral damage because it falls under the google.com domain, blocked since 2010.

2017-lu-accessing §2 ip-blockingdns-poisoningdpikeyword-filtering